Recently, the range of uses for primary batteries such as alkaline-manganese batteries is widened. In addition to the conventional uses for low-load discharge, the uses for devices which require high-load discharge performance, such as for example digital still cameras, are increasing.
Therefore, for improvement in high-load discharge performance without deterioration in low-load discharge performance, the inventors of the present invention have been examining uses of lambda-manganese dioxide. There have been proposed, for example, methods to use lambda-manganese dioxide or to use a mixture of gamma-manganese dioxide (typically electrolytic manganese dioxide) and lambda-manganese dioxide in cathodes, as in U.S. Pat. No. 6,783,893 and US 2004/0058242. However, from the examination of the inventors of the present invention, clear effects could not be found in any of low-load discharge and high-load discharge. Additionally, although ITE Letters on Batteries, New Technologies & Medicine, Vol. 2, No. 3, pp.341-348 (2001) notes the method in which lambda-manganese dioxide is added to electrolytic manganese dioxide for use, no details can be found regarding examination on the particle size of lambda-manganese dioxide, and no remarkable improvement in discharge performance is shown.
The use of the conventional lambda-manganese dioxide or the mixture of lambda-manganese dioxide and gamma-manganese dioxide improves high-load discharge performance. However, there are problems in that because in a low-load discharge, lambda-manganese dioxide particles expand toward a termination of the discharge and the expansion involves an expansion of the cathode mixture as well, ion migration in the cathode mixture is inhibited and discharge polarization is increased, leading to remarkable deterioration in low-load discharge performance. Alkaline batteries are not always used for those devices involving a high-load discharge. Therefore, it is extremely unfavorable if the discharge-time decreases when the alkaline batteries are used for devices that conventionally involve low-load discharge.